1. Technical Field
The present disclosure relates to an apparatus for treating spinal conditions, and, more particularly, to an expandable intervertebral implant and a method of use therefor.
2. Background of Related Art
The human spine includes thirty-three vertebrae. The vertebrae interlock with one another to form a spinal column. Each vertebra has a cylindrical bony body (vertebral body), two pedicles extending from the vertebral body, a lamina extending from the pedicles, two wing-like projections extending from the pedicles, a spinous process extending from the lamina, a pars interarticularis, two superior facets extending from the pedicles, and two inferior facets extending from the lamina. The vertebrae are separated and cushioned by thin pads of tough, resilient fiber known as inter-vertebral discs. Inter-vertebral discs provide flexibility to the spine and act as shock absorbers during activity. A small opening (foramen) located between each vertebra allows passage of nerves. When the vertebrae are properly aligned, the nerves pass through without a problem. However, when the vertebrae are misaligned or a constriction is formed in the spinal canal, the nerves get compressed and may cause back pain, leg pain, or other neurological disorders.
Disorders of the spine that may cause misalignment of the vertebrae or constriction of the spinal canal include spinal injuries, infections, tumor formation, herniation of the inter-vertebral discs (i.e., slippage or protrusion), arthritic disorders, and scoliosis. In these pathologic circumstances, surgery may be tried to either decompress the neural elements and/or fuse adjacent vertebral segments. Decompression may involve laminectomy, discectomy, or corpectomy. Laminectomy involves the removal of a part of the lamina, i.e., the bony roof of the spinal canal. Discectomy involves removal of the inter-vertebral discs. Corpectomy involves removal of the vertebral body as well as the adjacent inter-vertebral discs.
A number of spinal surgical devices may be used to promote bony fusion after decompressing the spinal nerves. For instance, surgeons often replace the diseased vertebral tissue with one or more spinal cages and bone support matrix. Spinal cages support adjacent vertebral segments, while furthering spinal fusion of adjacent vertebral bodies. Scientists and clinicians have developed a number of devices and methods for decompressing spinal nerves. Improvements to this methods and devices are nevertheless still possible.
Furthermore, intervertebral spacer implants used as a stand-alone device or provided in an assembly including a retention mechanism to help alleviate expulsion and movement of the implant when placed in the spine, are well known. Such implant assemblies are advantageous in providing an implant that is easier to insert in the spine. Such implant assemblies resist expulsion subsequent to implantation. Intervertebral spacer implant assemblies which include a spacer and a plate, where the plate comprises a supplemental or alternative retention mechanism having one or more holes in the anterior end of the plate that are directed toward the superior, inferior or both endplates of adjacent vertebrae are also known in the art. Such implants are used to stabilize and immobilize the spinal segments in the treatment of single or multi-level degenerative disc disease, spinal stenosis, and failed previous fusions, as well as other spine conditions.
One problem with such implant assembly/face plate combinations is that it is necessary to provide and inventory a plurality of sizes of both implants and face plates in order to accommodate the sizes required to treat a broad sampling of the patient population. Accordingly, a need exists for an implant assembly that can accommodate various dimensions of intervertebral space with reduced number of parts.